This project will further characterize the potassium transport systems of Escherichia coli. This is a very good model system for the study of potassium transport, since biochemical, physiological, and genetic methods can be used. There are many similarities between animal cell mitochondria and gram-negative bacteria such as E. coli, suggesting that information about potassium uptake in the bacteria can be used to explore the corresponding process in mitochondria. The major current goal of this project is the further characterization of the mechanism of energy coupling for ATP-driven bacterial potassium transport. Studies in vivo with suitable mutants will attempt to better define possibilities, while in vitro studies have as their goal to develop an in vitro assay for ATP-driven transport. BIBLIOGRAPHIC REFERENCES: Rhoads, D. and Epstein, W. (1977) Energy Coupling to Net K ion Transport in Escherichia coli K-12. J. Biol. Chem. 252(4):1394-1401. Rhoads, D., Woo, A. and Epstein, W. (1977) Discrimination between Rb ion and K ion by Escherichia coli. Biochemica et Biophysica Acta (in press).